Long=term objectives are to reduce morbidity and mortality due to congenital Toxoplasma gondii infection by improved use of antimicrobial agents and understanding its pathogenesis. Our specific aim is to determine optimal methods to evaluate, treat and provide follow up care for children suffering from congenital toxoplasmosis. Our ongoing, prospective, randomized treatment trial will be continued, as initially planned, to determine early and long term outcome for treated children, including children who have been treated in utero. Cognitive, motor, ocular and audiologic outcome will be determined following treatment with one of two dosages of pyrimethamine plus sulfadiazine during the first year of life. Evaluation of the cohort of older, untreated "historical patient" children with retinal disease provides an ideal and well characterized group of patients for a future randomized, placebo-controlled study of effect of antimicrobial agents active against encysted bradyzoites on relapsing chorioretinitis. These studies will contribute to determining how to best provide medical care to children afflicted with congenital toxoplasmosis.